Coatings

ABSTRACT

This invention relates to coating a surface wherein the coated surface inhibits foulants such as cell and/or protein and/or prion adhesion or formation. In particular, the coated surface may be part of a medical device which inhibits bacterial adhesion and colonisation, thrombus formation and/or prion, blood protein and/or protein formation.

RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §371 from PCTApplication No. PCT/GB03/003007, filed in English on Jul. 10, 2003,which claims the benefit of Great Britain Application Ser. No. 0215916.8filed on Jul. 10, 2002, the disclosures and contents of which areincorporated by reference herein in their entireties.

FIELD OF THE INVENTION

This invention relates to coating a surface wherein the coated surfaceinhibits foulants such as cell and/or protein and/or prion adhesion orformation. In particular, the coated surface may be part of a medicaldevice which inhibits bacterial adhesion and colonization, thrombusformation and/or prion, blood protein and/or other protein formation.

BACKGROUND OF THE INVENTION

A problem which exists in the art is that implanted medical devices areprone to bacterial adhesion and colonization on their surface. Implantedmedical devices are also susceptible to thrombus formation and prion,blood protein and/or other protein formation.

Infections arising from the use of implanted medical devices, such asheart valves, stents, catheters, joint prostheses, intraocular lensesand dental implants etc. are associated with increased morbidity andmortality, prolonged hospitalisation, patient discomfort and increasedmedical costs. Progress in the area of anti-microbial treatment has beenof limited success. For example, infection reportedly occurs in up to13.9% of patients following stabilization of open fractures and in about2% of patients who receive joint prostheses. Due to infection,prosthetic valve endocarditis remains one of the most dangerous andlife-threatening complications following heart valve replacement.Mortality rates as high as 75% have been reported. Furthermore, urinaryor vascular catheters are associated with a high rate of infection,about 7.6 infections per 1000 catheter-days.

Anti-microbial coatings for medical devices have recently emerged as apotentially effective method for preventing device-related infections.This is achieved by releasing anti-microbial agents from a coating tokill bacteria or to inhibit bacterial colonization. Some medical devicessuch as prosthetic heart valve sewing rings, stents, catheters andorthopaedic implants coated with anti-microbial agents have beenreported. The anti-microbial agents used are silver, antibioticscombined with minocycline and rifampin, and surfactants etc. (Haley R W,“Estimating the Extra Charges and Prolongation of Hospitalisation Due toNosocomial Infections: A Comparison of Methods”. J. Infect. Dis.,141:248-257 (1980); DiTizio V, Ferguson G W, Mittelman M W, Khoury A E,Bruce A W, DiCosmo F, “A Liposomal Hydrogel for the Prevention ofBacterial Adhesion to Catheters”, Biomaterials, 19:20, 1877-1884 (1998);Illingworth B L, Tweden K, Schroeder R E, Cameron J D, “In Vivo Efficacyof Silver-Coated (Silzone (TM)) Infection-Resistant Polyester FabricAgainst a Biofilm-Producing Bacteria, Staphylococcus Epidermidis”,Journal Of Heart Valve Disease, 7: (5) 524-530 (1998); Stamm W E.“Catheter-Associated Urinary Tract Infections: Epidemiology,Pathogenesis, and Prevention”, Am. J. Med., 91:65-71 (1991); Darouiche,R O, “Prevention of Vascular Catheter-Related Infections”, TheNetherlands Journal of Medicine 55:92-99 (1999)).

However, the currently available antimicrobial coatings have theproblems of poor abrasion and poor corrosion resistance, limitedbiocompatibility and other adverse side effects. For example, the localcytotoxicity of silver-coated catheter cuffs and orthopaedic implants onhuman fibroblast cells has been observed.

Furthermore, there has been a growing understanding that the generationof wear debris due to friction at articulating surfaces or the releaseof metal ions can lead to severe cell response and bone resorption orosteolysis, giving rise to premature failure of implants.

Blood contacting devices often suffer from thrombus formation due tolimited haemocompatibility. The interaction of an implanted materialsurface with blood stimulates platelet activation, leading to bloodcoagulation and thrombus formation. Numerous studies have been done toreduce thrombus formation by coating device surfaces with diamond-likecarbon or bioactive materials. Diamond-like carbon shows great promiseas a durable, wear- and corrosion-resistant coating for biomedicalimplants. Despite these favourable results and continuous technicalimprovements, the application of stents, artificial arteries andvascular catheters etc. is still limited by subacute occlusion andrestenosis due to thrombus formation, especially in low flow andstagnation zones. The initial step of thrombus formation onblood-contacting biomaterials is known to be adsorption of bloodproteins followed by platelet adhesion. However, diamond-like carboncoatings cannot inhibit blood protein adhesion to their surfacessignificantly.

Cleaning, disinfection and sterilization of surgical instruments iscrucial as they are in direct contact with blood and internal organs. Itis critical that prior to any disinfection or sterilisation procedurethat all items undergo a thorough physical cleaning. However, the stainson the surfaces of surgical devices from contamination are not easilyremoved. Prion (a microscopic protein particle similar to a virus butlacking nucleic acid, thought to be the infectious agent responsible forscrapie and certain other degenerative diseases of the nervous system)diseases constitute a unique infection control problem because prionsexhibit unusual resistance to conventional chemical and physicaldecontamination methods. Recommendations to prevent cross-transmissionof infection from medical devices contaminated by Creutzfeldt-Jakobdisease (CJD) have been based primarily on prion inactivation studies.On the basis of the scientific data, only critical (e.g. surgicalinstruments) and semicritical devices contaminated with high-risk tissue(i.e. brain, spinal cord and eye tissue) from high-risk patients—thosewith known or suspected infection with CJD—require special treatment.The whole issue of contamination has become highly topical recently withconcerns about the spread of CJD through surgical and butchers'instruments (e.g. knives). So far no attempts have been made to developCJD-resistant surgical instruments.

It is an object of at least one aspect of the present invention toobviate/mitigate one or more of the aforementioned disadvantages.

It is a further object of the present invention to provide coatings withanti-microbial properties and/or improved haemocompatibility.

It is yet a further object of the present invention to provide amaterial which may be coated on a surface or substrate which is capableof inhibiting any of the following from adhering to surfaces:microorganisms, platelets, proteins (blood protein or prion protein)and/or cells.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided amodified surface wherein the adhesion or attachment of particles to themodified surface has been minimised or prevented by adjusting theLifshitz-van der Waals (LW) surface free energy of an unmodified surfaceto be equal to or approximately equal to the Lifshitz-van der Waals (LW)surface free energy of particles in an environment surrounding thesurface when the modified surface is in use.

The particles may be foulants.

The particles may be selected from any of the following: cells,proteins, prions, bacteria, amino acids, nucleic acids, metallic basedcompounds, organometallics, organic compounds, inorganic compounds orany other type of discrete separate particles.

Typically, there is a surface with a Lifshitz-van der Waals (LW) surfacefree energy of γ^(LW) _(Surface) on which the adhesion or attachment ofparticles is minimised or prevented by modifying the surface free energyγ^(LW) _(Surface) of the surface in accordance with the Lifshitz-van derWaals (LW) surface free energy of the particles so that:γ^(LW) _(surface)≅γ^(LW) _(S,Min)wherein γ^(LW) _(S,min) is the minimum level of attachment to a surfaceS and is defined as follows:√{square root over (γ^(LW) _(S,Min))}=(½)(√{square root over (γ^(LW)_(particles))}+√{square root over (γ^(LW) _(environment))})

where γ^(LW) _(particles) is the LW surface free energy of particles,and γL^(LW) _(environment) is the LW surface free energy of anenvironment when the modified surface is in use.

In one example, the surface may be one which comes into contact withcells and/or proteins and/or prions within a living human or animalbody. In this example there is a surface with a Lifshitz-van der Waals(LW) surface free energy of γ^(LW) _(Surface) on which the adhesion orattachment of cells and/or proteins and/or prions is minimised orprevented by modifying the surface free energy γ^(LW) _(Surface) of thesurface in accordance with the Lifshitz-van der Waals (LW) surface freeenergy of the cells and/or proteins and/or prions so that:γ^(LW) _(surface)≅γ^(LW) _(S,Min)wherein γ^(LW) _(S,min) is the minimum level of attachment to a surfaceS and is defined as follows:√{square root over (γ^(LW) _(S,Min))}=(½)(√{square root over (γ^(LW)_(cells and/or proteins and/or prions))}+√{square root over (γ^(LW)_(solution and/or whole blood))})where γ^(LW) _(cells and/or proteins and/or prions) is the LW surfacefree energy of cells and/or proteins and/or prions, and γ^(LW)_(solution and/or whole blood) is the LW surface free energy of asolution and/or of whole blood.

Conveniently, the surface is modified with a coating of modifieddiamond-like carbon (DLC), Ag—PTFE-surfactant or Ni—Cu—P—PTFE whereinthe coated surface inhibits bacterial adhesion and colonisation,thrombus adhesion to the surface and foulant formation (i.e. particleformation) such as prion, blood protein and/or other protein formation.

Typically, the diamond-like carbon (DLC) is modified by incorporatingelements selected from any of the following: halogens such as fluorine,chlorine and bromine; Group IV elements such as silicon and germanium;Group V elements such as nitrogen and phosphorous; Group VI elementssuch as oxygen and sulphur; and transition metals such as titanium,tantalum, tungsten and niobium. The elements may be present in an amountof 0-40% by weight. The elements may be incorporated into thediamond-like carbon by co-sputtering.

Alternatively, the elements are incorporated into the diamond-likecarbon (DLC) using reactive gases such as fluorinous monomers (e.g.C₂F₂, C₂F₄ and HCF₃), silicon organic monomers (e.g. Si(CH₃)₄) gaseoushydrocarbons (eg. C₂H₂) and gases such as O₂ and N₂.

The modified diamond-like carbon (DLC) may be deposited using any of thefollowing methods: microwave plasma deposition, plasma-enhanced vapourdeposition, plasma-induced cold deposition, magnetron sputtering and ionbeam-assisted deposition.

The surfactant in the Ag—PTFE-surfactant may be non-ionic, anionic orcationic.

Typically, the ratio of Ag:PTFE:surfactant is about 80-60%:10-39%:1-10%by weight and preferably 75%:22%:3% by weight.

Preferably, the surfactant in the Ag—PTFE-surfactant is selected fromany of the following: C₂₀H₂₀F₂₃N₂O₄I, and polyoxyethylene nonylphenylether.

The polyoxyethylene nonylphenyl ether may be selected from any of thefollowing:

4-(C₉H₁₉)C₆H₄(OCH₂CH₂)_(n)OH, n≈12, Hydrophile Lipophile Balance(HLB)=12; 4-(C₉H₁₉)C₆H₄(OCH₂CH₂)_(n)OH, n≈40, HLB=17.8;4-(C₉H₁₉)C₆H₄(OCH₂CH₂)_(n)OH, n≈100, HLB=19; and(C₉H₁₉)₂C₆H₃(OCH₂CH₂)_(n)OH, n≈150, HLB=19.

Typically, the Ag—PTFE-surfactant coating is obtained using anelectroless plating technique.

Alternatively, the Ag—PTFE-surfactant coating is obtained using anelectroless plating technique.

Typically, the Ni—Cu—P—PTFE coating is obtained using an electrolessplating technique.

Alternatively, the Ni—Cu—P—PTFE coating is obtained using anelectroplating technique.

Typically, the ratio of Ni:Cu:P:PTFE is about 97-40%:1-20%:1-20%:1-20%by weight. In one particular example, for inside a body the Ni:Cu:P:PTFEratio may be 80%:11%:4%:5% by weight. It should be realised that forinside different bodies a different ratio may be required due toslightly different environments.

Conveniently, the surface which is coated is selected from any of thefollowing: healthcare products; dental care products; baby careproducts; personal hygiene products; consumer cleaning and disinfectantproducts; institutional and industrial cleaning products; foodpreparation devices and packaging; water storage products; watertreatment products; water delivery systems; biofilm sensitive systems;and laboratory and scientific equipment.

The coated surface may be part of a medical device. In particular, themedical device may be selected from any of the following: endoscopes andaccessories; ophthalmic equipment; dental equipment; surgicalinstruments; heart valves; stents; catheters; joint prostheses;intraocular lenses, dental implants, electrodes and cable equipment.

The coated surface may inhibit the following bacteria: Staphylococcusepidermidis, Staphylococcus aureus, Pseudomonas aeruginosa, Escherichiacoli, Candida albicans or any other microorganisms which could causedevice-related infections.

According to a second aspect of the present invention there is provideda method for preventing or minimising the adhesion or attachment ofparticles to a surface by modifying the surface to form a modifiedsurface so that the Lifshitz-van der Waals (LW) surface free energy ofthe modified surface is equal to or approximately equal to theLifshitz-van-der Waals (LW) surface free energy of particles in anenvironment surrounding the surface.

According to a third aspect of the present invention there is provided adevice comprising a modified surface wherein the modified surfaceprevents or minimises the attachment of particles to the modifiedsurface.

Typically, the device is a medical device. In particular, the medicaldevice may be selected from any of the following: endoscopes andaccessories; ophthalmic equipment; dental equipment; surgicalinstruments; heart valves; stents; catheters; joint prostheses;intraocular lenses; dental implants; electrodes and cable equipment.

According to a fourth aspect of the present invention there is provideda method of modifying a surface wherein the surface is modified so thatthe adhesion or attachment of particles to the modified surface has beenminimised or prevented by adjusting the Lifshitz-van der Waals (LW)surface free energy of an unmodified surface to be equal to orapproximately equal to the Lifshitz-van der Waals (LW) surface freeenergy of particles in an environment surrounding the surface when themodified surface is in use.

According to a fifth aspect of the present invention there is provideduse of a device comprising a modified surface according to the firstaspect wherein the modified surface prevents or minimises the attachmentof particles to the modified surface.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described, by way ofexample only, with reference to the accompanying drawings in which:

FIG. 1 is a graph showing the surface free energy for a variety ofdiamond-like carbon (DLC) coatings;

FIG. 2 is a microscope image of the amount of bacteria on a diamond-likecarbon (DLC) coated surface according to the prior art;

FIG. 3 is a microscope image of the amount of bacteria on a modifieddiamond-like carbon (DLC) coated surface comprising fluorine accordingto a first embodiment of the present invention; and

FIG. 4 is a microscope image of the amount of bacteria on aAg—PTFE-C₂₀H₂₀F₂₃N₂O₄I surfactant coated surface according to a secondembodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The first theory used to explain interactions involving colloidalparticles or bacterial adhesion was the DLVO theory, named after fourscientists, Deryagin, Landau, Verwey and Overbeek. According to the DLVOtheory, the principal interaction forces determining hetero-coagulationinclude a Lifshitz-van der Waals (LW) interaction component, anelectrostatic double-layer component (EL), a Lewis acid-base component(AB), and a Brownian motion component (Br). The theory involves severalcomplex equations and has been used as a qualitative model (Bos R,Busscher H J, Role of Acid-Base Interactions on the Adhesion of OralStreptococci and Actinomyces to Hexadecane and Chloroform—Influence ofDivalent Cations and Comparison Between Free Energies of Partitioningand Free Energies Obtained by Extended DLVO Analysis, Colloids AndSurfaces B-Biointerfaces, Vol. 14, pp. 169-177(1999)).

In the present application the DLVO theory has been extended. Theextended DLVO theory showed that the adhesion or attachment of particlessuch as cells and/or proteins and/or prions to a surface is minimised orprevented if the Lifshitz-van der Waals (LW) surface free energy of thesurface, γ^(LW) _(surface) is modified so that it is equal orapproximately equal to γ^(LW) _(s,min) as defined below:√{square root over (γ^(LW) _(S,Min))}=(½)(√{square root over (γ^(LW)_(particles))}+{square root over (γ^(LW) _(environment))})where γ^(LW) _(particles) is the LW surface free energy of particles andγ^(LW) _(environment) is the surface free energy of the environment.

In one example and for inside a particular human or animal body theLifshitz-van der Waals (LW) surface free energy may be defined asfollows:√{square root over (γ^(LW) _(S,Min))}=(½)(√{square root over (γ^(LW)_(cells and/or proteins and/or prions))}+√{square root over (γ^(LW)_(solution and/or whole blood))})where γ^(LW) _(cells and/or proteins and/or prions) is the LW surfacefree energy of cells and/or proteins and/or prions and γ^(LW)_(solution and or whole blood) is the LW surface free energy of asolution and/or of whole blood. It should be realised that insidedifferent bodies and inside different areas of the body there will bedifferent surface free energies.

Based on this theoretical model, it was derived that the time requiredto form a mono-layer of particles such as cells and/or proteins and/orprions on a surface is as follows:time=f(C/|√{square root over (γ^(LW) _(Surface))}−√{square root over(γ^(LW) _(S,min))}|)where C is constant which is dependant on the properties of attachedparticles. The equation indicates that if the LW surface free energy,γ^(LW) _(surface), is equal to γ^(LW) _(S,min) (i.e. γ^(LW)_(surface)≅γ^(LW) _(s,min)), the time required to form a mono-layer ofparticles such as cells and/or proteins and/or prions on a surface isinfinite.

In general, the LW surface free energy of, for example, a medical deviceis unlikely to be equal to γ^(LW) _(S,min). The end result is that theLW surface free energy of devices therefore have to be altered by asurface modification technique, so that γ^(LW) _(Surface)≅γ^(LW)_(S,min).

The present invention relates to three different types of coating:modified diamond-like carbon coatings, Ag—PTFE-surfactant coatings andNi—Cu—P—PTFE nano-composite coatings.

By modifying diamond-like carbon the interaction forces between amodified diamond-like carbon surface and cells and/or proteins and/orprions may be altered so as to prevent bacterial adhesion andcolonization, thrombus formation and inhibit prion, blood protein and/orother protein formation. This may be predicted using the above-mentionedequations.

The diamond-like carbon is modified by incorporating elements selectedfrom any of the following: halogens such as fluorine, chlorine andbromine; Group IV elements such as silicon and germanium; Group Velements such as nitrogen and phosphorous; Group VI elements such asoxygen and sulphur; and transition metals such as titanium, tantalum,tungsten and niobium. The incorporated elements are present in an amountof 0-40% by weight and are chemically and/or physically bonded to thediamond-like carbon.

The elements are incorporated into the diamond-like carbon byco-sputtering or by adding reactive gases such as fluorinous monomers(e.g. C₂F₂, C₂F₄, HCF₃), silicon organic monomers (e.g. Si(CH₃)₄)gaseous hydrocarbons (e.g. C₂H₂) and gases such as O₂ and N₂ to theworking gas during the coating process. The working gas is for example,argon. A variety of deposition methods may be used including microwaveplasma deposition, plasma-enhanced vapour deposition, plasma-inducedcold deposition, magnetron sputtering and ion beam-assisted depositionetc.

A plasma enhanced (or activated) chemical vapour deposition process isdescribed as follows. Diamond-like carbon coatings may be modified bythe deposition of elements (e.g. fluorinous monomers (e.g. C₂F₂, C₂F₄and HCF₃); silicon organic monomers (e.g. Si(CH₃)₄,) gaseoushydrocarbons (e.g. C₂H₂) and gases such as O₂ and N₂ in a plasmaenhanced (or activated) chemical vapour deposition process. Thedeposition system mainly consists of a tube reactor with a radiofrequency (rf) generator, a power electrode, a self-bias device and aturbo pump. A typical power density during the deposition is about0.1-0.8 W/cm² with negative self-bias of about 400-1800 V. The gas flowrate is about 10˜150 cm³/min. The gas ratio (e.g. C₂F₄:C₂H₂ orHCF₃:C₂H₂) is about 0˜25. Before deposition, the samples need cleaningby argon etching.

A combined radio frequency (rf) plasma and magnetron sputteringtechnique is described as follows. Modified diamond-like carbon coatingscontaining the required elements (e.g. Ti, O, F etc.) may be producedusing a combined radio frequency (rf) plasma and magnetron sputteringprocess from a mixture (e.g. acetylene and Ti(C₂H₅O)₄) in a high vacuumsystem with a base pressure of more than 2×10⁶ Pa. The coatings may bedeposited on various substrates, such as stainless steel. The rfgenerator output may be regulated to yield a constant sample self-biasof about −400˜−600 V. Sample substrates are cleaned ultrasonically in a1:1 ratio of acetone/ethanol prior to film deposition. After plasmacleaning for 2 mins at 3 Pa argon pressure, the depositions areperformed with a total mixture pressure of 2 Pa. Adjusting DC sputterpower between 30 and 200 V and the element ratio in the mixture, enablesdeposited films with different element (e.g. Ti, O, F etc)concentrations ranging from 1 to 25% by weight. The substratetemperature during deposition is about 150° C.

Ion beam-assisted deposition (IBAD) is a vacuum deposition process thatcombines physical vapour deposition (PVD) with ion beam bombardment. Avapour of coating atoms is generated with an electron beam evaporatorand deposited on a substrate. Ions, typically gaseous species, aresimultaneously extracted from a plasma and accelerated into a growingPVD film at energies of several hundred to several thousand electronVolts. The ions interact with coating atoms, driving them into thesubstrate and producing a graded material interface, which enhancesadhesion. The major processing parameters are shown in the Table below:

Base pressure 7~9 × 10⁴ Pa Ar⁺ sputtering ion energy 1~5 keV Ar⁺sputtering ion current 30~70 mA Hydrocarbon bombarding ion energy200~1000 eV Hydrocarbon bombarding ion current 8~15 mA Depositiontemperature <80° C.

FIG. 1 shows that the surface energy of diamond-like carbon coatings maybe adjusted over a wide range in a well-controlled manner by theincorporation of elements such as F, Si, O, N or Ti into the surface.This means that the surface energy of modified diamond-like carboncoatings can be adjusted to a required value. Cells and/or proteinsand/or prions may therefore be inhibited from attachment or adhesion.

The modified diamond-like carbon is found to have improved mechanicalstability over normal diamond-like carbon.

A Ag—PTFE-surfactant coating is also used as an anti-bacterial coating.The incorporation of PTFE and a surfactant into a metal matrix takesadvantage of different properties of the metal, the PTFE and thesurfactant. The ratio of Ag:PTFE:surfactant is about 80-60%:10-39%:1-10%by weight and is preferably 75%:22%:3% by weight.

Suitable surfactants are selected from a C₂₀H₂₀F₂₃N₂O₄I compound or apolyoxyethylene nonylphenyl ether. The polyoxyethylene nonylphenyl etheris selected from any of the following:

4-(C₉H₁₉)C₆H₄(OCH₂CH₂)_(n)OH, n≈12, Hydrophile Lipophile Balance(HLB)=12; 4-(C₉H₁₉)C₆H₄(OCH₂CH₂)_(n)OH, n≈40, HLB=17.8;4-(C₉H₁₉)C₆H₄(OCH₂CH₂)_(n)OH, n≈100, HLB=19; and(C₉H₁₉)₂C₆H₃(OCH₂CH₂)_(n)OH, n≈150, HLB=19.

The Ag—PTFE-surfactant coating is obtained using an electroless platingtechnique which merely comprises immersing the device or part of thedevice to be coated. A thickness of about 2-5 micrometres is obtained.

The third type of coating is Ni—Cu—P—PTFE which is obtained via asimilar electroless plating technique to the Ag—PTFE-surfactant coating.The ratio of the different constituents is selected in order to obtainthe value of γ^(LW) _(s,min). For various particles their γ^(LW)_(s,min) values may be different, so the ratio of the constituents maybe different.

Products which are coated using modified diamond-like carbon coatings,Ag—PTFE-surfactant coatings and Ni—Cu—P—PTFE nanocomposite coatings maybe selected from any of the following: healthcare products; dental careproducts; baby care products; personal hygiene products; consumercleaning and disinfectant products; institutional and industrialcleaning products; food preparation devices and packaging; water storageand water treatment products and delivery systems; biofilm sensitivesystems; and laboratory and scientific equipment.

In particular, medical devices selected from any of the following may becoated: endoscopes and accessories; opthalmic equipment; dentalequipment; and surgical instruments; heart valves; stents; catheters;joint prostheses; intravascular lenses and dental implants.

EXAMPLES Comparative Example 1

FIG. 2 is a microscope image of the amount of bacteria found on asurface of a medical device with a diamond-like carbon coating (i.e.unmodified). There is a bacteria density of 602000 cells/cm².

Example 1

FIG. 3 is a microscope image of the amount of bacteria found on asurface of a medical device with a coating of modified diamond-likecarbon which comprises about 4% fluorine. There is a bacteria density of407 cells/cm². A combined radio frequency (rf) plasma and magnetronsputtering technique is used to form the coating which is about 2micrometers thick.

Example 2

FIG. 4 is a microscope image of the amount of bacteria found on asurface of a medical device with a Ag—PTFE-C₂₀H₂₀F₂₃N₂O₄ surfactantcoating of about 4 micrometers thick. The ratio of Ag:PTFE:surfactant is75%:22%:3% by weight. There is a bacteria density of 614 cells/cm².

To form this coating the following electroless plating technique isused:

Procedures Conditions 1. Alkaline cleaning NaOH: 20~30 g/l; Na₂CO₃:25~30 g/l; Na₃PO₄: 25~35 g/l; Na₂SiO₃: 5~10 g/l; Temperature: 60~80° C.,Time: 5~10 min. 2. Rinsing With water. Room temperature. 3. Cathodicelectrocleaning NaOH: 25~35 g/l; Na₂CO₃: 25~30 g/l; Na₃PO₄: 25~35 g/l;Na₂SiO₃: 5~10 g/l; voltage: 5~7 V; Room temperature; Time: 2~3 min. 4.Rinsing With water. Room temperature. 5. Pickling HCl (30%): H₂O = 1:1;Room temperature. Time: 0.5~1 min. 6. Activation (to coat a NiCl₂.6H₂O:200~400 g/l; HCl super-thin layer Ni) (30%): 75~200 ml/litre; Anodeplates: Ni; Cathodic current: 2~3 A/dm²; Room temperature; Time: 1 min.7. Electroless plating Ni—P NiCl₂.6H₂O: 20~30 g/l; Na₃C₆H₅O₇.6H₂O: 15~30g/l; NaH₂PO₂: 15~35 g/l; C₃H₆O₃: 20~30 g/l; Temperature: 85~90° C.; pH:4.6~5.0 8. Rinsing With water. Room temperature. 9. Electroless platingwith 30~90° C., pH: 4.8~9.0 Ag-PTFE surfactant 10. Rinsing With water.Room temperature.

Example 3

The following electroless plating technique is used to form a coating ofNi—Cu—P—PTFE nano-composite. The ratio of Ni:Cu:P:PTFE is 80%:11%:4%:5%by weight.

Procedures Conditions 1. Alkaline cleaning NaOH: 20~30 g/l; Na₂CO₃:25~30 g/l; Na₃PO₄: 25~35 g/l; Na₂SiO₃: 5~10 g/l; Temperature: 60~80° C.,Time: 5~10 min. 2. Rinsing With water. Room temperature. 3. Cathodicelectrocleaning NaOH: 25~35 g/l; Na₂CO₃: 25~30 g/l; Na₃PO₄: 25~35 g/l;Na₂SiO₃: 5~10 g/l; voltage: 5~7 V; Room temperature; Time: 2~3 min. 4.Rinsing With water. Room temperature. 5. Pickling HCl (30%): H₂O = 1:1;Room temperature. Time: 0.5~1 min. 6. Activation (to coat a NiCl₂.6H₂O:200~400 g/l; HCl super-thin layer Ni) (30%): 75~200 ml/litre; Anodeplates: Ni; Cathodic current: 2~3 A/dm²; Room temperature; Time: 1 min.7. Electroless plating Ni—P NiCl₂.6H₂O: 20~30 g/l; Na₃C₆H₅O₇.6H₂O: 15~30g/l; NaH₂PO₂: 15~35 g/l; C₃H₆O₃: 20~30 g/l; Temperature: 85~90° C.; pH:4.6~5.0 8. Rinsing With water. Room temperature. 9. Electroless platingwith 85~90° C., pH: 4.8~5.0 Ni—Cu—P-PTFE 10. Rinsing With water. Roomtemperature.

1. A modified surface wherein the adhesion or attachment of cells,proteins and/or prions to the modified surface has been minimised orprevented by adjusting the Lifshitz-van der Waals (LW) surface freeenergy of an unmodified surface to be equal to or approximately equal tothe Lifshitz-van der Waals (LW) surface free energy of the cells,proteins and/or prions in a solution and/or whole blood surrounding thesurface, wherein the surface is modified with a coating of modifieddiamond-like carbon (DLC), wherein the coated surface inhibits bacterialadhesion and colonisation, thrombus adhesion to the surface and foulantformation, wherein the surface is one which comes into contact withcells, proteins and/or prions within a living human or animal body,wherein the LW surface free energy of the modified surface is in a rangeof about 25 mN/m to about 45 mN/m, and wherein the adhesion orattachment of said cells, proteins and/or prions is minimised orprevented by modifying the surface free energy γ^(LW) _(surface) of thesurface in accordance with the Lifshitz-van der Waals (LW) surface freeenergy of the cells, proteins and/or prions so that:γ^(LW) _(surface≈γ) ^(LW) _(S,Min) wherein γ^(LW) _(S,Min) is theminimum level of attachment to a surface S and is defined as follows:√{square root over (γ^(LW) _(S,Min))}=(½)(√{square root over (γ^(LW)_(cells and/or proteins and/or prions))}+√{square root over (γ^(LW)_(solution and/or whole blood))}) where _(γ) ^(LW)_(cells, proteins and/or prions) is the LW surface free energy of thecells, proteins and/or prions, and _(γ) ^(LW)_(solution and/or whole blood) is the LW surface free energy of thesolution and/or of whole blood.
 2. A modified surface according to claim1 wherein the surface is modified with a coating of diamond-like carbon(DLC) which is modified by incorporating elements selected from any ofthe following: halogens; Group IV elements; Group V elements; Group VIelements; and transition metals.
 3. A modified surface according toclaim 2 wherein the elements are present in an amount of 0-40% byweight.
 4. A modified surface according to claim 2 wherein the elementsincorporated into the diamond-like carbon by co-sputtering.
 5. Amodified surface according to claim 2 wherein the elements areincorporated into the diamond-like carbon (DLC) using reactive gases,silicon organic monomers, gaseous hydrocarbons, O₂, and/or N₂.
 6. Amodified surface according to claim 1 wherein the modified diamond-likecarbon (DLC) is deposited using any of the following methods: microwaveplasma deposition, plasma-enhanced vapour deposition, plasma-inducedcold deposition, magnetron sputtering and ion beam-assisted deposition.7. A modified surface according to claim 1 wherein the modified surfaceis part of a medical device.
 8. A modified surface according to claim 7wherein the medical device is selected from any of the following:endoscopes and accessories; ophthalmic equipment; dental equipment;surgical instruments; heart valves; stents; catheters; joint prostheses;intraocular lenses, dental implants, electrodes and cable equipment. 9.A modified surface according to claim 1 wherein the modified surfaceinhibits the following bacteria: Staphylococcus epidermidis,Staphylococcus aureus, Psuedomonas aeruginosa, Escherichia coli, Candidaalbicans or any other microorganisms which could cause device-relatedinfections.
 10. A device comprising a modified surface according toclaim 1.